The semiconductor integrated circuit (IC) industry has experienced rapid growth. Technological advances in IC materials and design have produced generations of ICs where each generation has smaller and more complex circuits than the previous generation. In the course of IC evolution, functional density (i.e., the number of interconnected devices per chip area) has generally increased while geometry size (i.e., the smallest component (or line) that can be created using a fabrication process) has decreased. This scaling down process generally provides benefits by increasing production efficiency and lowering associated costs. Such scaling down has also increased the complexity of processing and manufacturing ICs and, for these advances to be realized, similar developments in IC processing and manufacturing are needed.
Field effect transistors (FETs) have been used in conventional IC design. Due to shrinking technology nodes, high-k (HK) dielectric material and metal are often considered to form a gate stack for a FET. Integration issues exist when forming various HK/metal-gate (MG) FETs onto a single IC chip, such as a HK/MG of p-type FET core, n-type FET core, input/output nFET, input/output pFET, and high-resistor. Thus, a process that provides flexibility and feasibility to fabricate various HK/MG structures is desired.